Seven and a half years after the US intervention in Afghanistan, it is little surprise that questions about its purpose have abounded. In that light, the Obama administration's clarification of its primary goal in the country - to "disrupt, dismantle and defeat" al-Qaida - is welcome. The task of discerning the "defeat" of al-Qaida may be near impossible, but the new US policy linking the conflict in Afghanistan with the situation in Pakistan is a step in the right direction.

The strategy review, presented at the end of last month, rightly emphasises links between the Afghan insurgency and its access to sanctuaries in Pakistan; the importance of reducing tensions between Pakistan and India (with the implied reference to Kashmir); and a redoubling of efforts to build up the Afghan security forces.

There is a welcome demand for a more accountable Afghan government and recognition that "rampant corruption" undermines its legitimacy; improved sub-national governance; a crackdown on corruption; and clear benchmarks to ensure that international assistance is used for the benefit of the Afghan people, combined with an acknowledgment that much development assistance is being spent on international consultants and overheads.

And it is surely sensible to back attempts to reconcile those Taliban elements believed to be fighting less out of ideological conviction than local grievances or lack of employment. Such talks must not, of course, provide a means for the return of "medieval rule", nor harm the quest for human rights and the advancement of women. Yesterday's demonstration in Kabul reminds us that women's rights are far from guaranteed in the new Afghanistan.

But is greater US involvement the answer? At the Bonn conference in 2001 some of us favoured a deeper UN footprint out of a conviction that, after 22 years of conflict, international forces would be welcomed by Afghans, ready for a period of international tutelage to rebuild their country and be rid not only of the Taliban but also of the Northern Alliance warlords. The opportunity was lost. And it is too late to revive it now.

If more US troops leads, as unfortunately seems only too likely, to more civilian casualties, it will backfire. Afghans increasingly resent the international military presence and react with growing anger at reports of civilian deaths, night searches of homes, arbitrary arrests and the indefinite detention of suspects by the US military.

Regrettably there is as yet no commitment by the administration to abide by the Geneva conventions and additional protocols, or to close US detention centres, where conditions are at least as harsh to those in Guantánamo. Nor is there a promise to start negotiations with the Afghan government on a status of forces agreement that - like the one recently concluded in Iraq - would regulate the presence and conduct of US forces in Afghanistan.

Barack Obama has so far rightly ignored calls for an increase in the Afghan security forces to 400,000, opting for a 134,000-strong army and 82,000 police. The emphasis should be on quality; expanding security forces without parallel efforts to build civilian institutions risks handing Afghanistan to a future military-led government. Indeed, the forthcoming presidential elections present a major security and political challenge. To ensure a level playing field urgent measures are needed, including special security protection for presidential candidates.

President Karzai's mandate constitutionally ends on 22 May, months before the proclamation of the winner of the August elections. The supreme court has backed the president's decision to stay on, but its competence is challenged on constitutional grounds. Given the disputed independence of the election commission, a UN-agreed consensus among the major candidates and political forces on how to proceed is essential. Otherwise there is every risk that the outcome will be widely regarded as fraudulent, leading to deepening ethnic polarisation, widespread cynicism about electoral politics and a president divested of legitimacy - all excellent news for the Taliban.

• Francesc Vendrell was the EU special representative for Afghanistan, 2002-2008, and the UN secretary general's personal representative for Afghanistan, 2000-2001